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From: "Jan Beulich" <jbeulich@novell.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: <mingo@elte.hu>, <tglx@linutronix.de>, <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] x86: bitops asm constraint fixes
Date: Fri, 14 Mar 2008 08:09:40 +0000	[thread overview]
Message-ID: <47DA40D4.76E4.0078.0@novell.com> (raw)
In-Reply-To: <47DA2E6F.5080907@zytor.com>

>>> "H. Peter Anvin" <hpa@zytor.com> 14.03.08 08:51 >>>
>Jan Beulich wrote:
>> 
>> I'd really like understand, though, what the policy of (not) having a
>> "memory" clobber in these operations is - currently, this appears to
>> be totally inconsistent. Also, many comments of the non-atomic
>> functions say those may also be re-ordered - this contradicts the use
>> of "asm volatile" in there, which again I'd like to understand.
>> 
>
>In general, proper "m" constraints are better than "memory" clobbers, 
>since they give gcc more information.  Note that the "m" constraint 
>doesn't actually have to be *manifest* in the assembly string.

... which is the case with the patch applied.

So am I taking this as 'yes, a proper re-write of these routines is
worthwhile'? But - you didn't comment on the other issues raised,
so before getting to that I'll have to wait to see what's the reason
(if any) for the other anomalies.

Jan


  reply	other threads:[~2008-03-14  8:09 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-13  9:08 [RFC] x86: bitops asm constraint fixes Jan Beulich
2008-03-14  7:51 ` H. Peter Anvin
2008-03-14  8:09   ` Jan Beulich [this message]
2008-03-14 18:56 ` Jeremy Fitzhardinge
2008-03-17  9:08   ` Jan Beulich
2008-03-14 21:07 ` Chuck Ebbert
2008-03-17  9:16   ` Jan Beulich
2008-03-19 13:19     ` H. Peter Anvin
2008-03-21 13:54 ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2008-03-27  8:12 Jan Beulich
2008-03-27  8:41 ` Ingo Molnar
2008-04-14 12:53   ` Jan Beulich
2008-03-28 19:55 Jan Beulich
2008-04-14 13:31 Jan Beulich
2008-04-14 16:21 ` Jeremy Fitzhardinge
2008-04-15  7:03   ` Jan Beulich

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